All questions answered

The following is a list of questions Donald E. Knuth answered
in "All Questions Answered" sessions and where answers are publicly
accessible. To add any questions answered or correct existing ones,
please write me an
email. Last update: 18th of May 2013

Questions answered

Rumor has it that there is an amazing pipe organ somewhere near where you live. Do you ever have anyone else… any other organist that plays that pipe organ and what's your favorite song played on it?[link]#

What kinds of problems do you feel that Google (or the industry at large) should be working on, but isn't?[link]#

With the increase in processing power and adoption of machine-independent high-level languages, it is a common perception that being 'close to the metal' doesn't matter anymore. What impact does this have on computer science as a field of study?[link]#

Literate programming has never really taken off, although some scripting languages have improved code readability somewhat. What, if anything, do you think has hindered its adoption?[link]#

This morning I used social search to find a name of a successful technique called propensity score matching. Sometimes I know that there is some mathematical concept that exists, but I don't know what the name of it is and I want to go find out about it. Integer sequences is a good example of a search technique that allows me to go find about it… [Don Knuth mentions OEIS.org]… Right, that's a good solution, but that does not solve all problems. How do you - when you know that there has been a mathematical concept that you stumbled across but don't know the name of it - find out what that name is so you don't have to go reinvent everything?[link]#

How many P!=NP 'proofs' have you seen? and what is your opinion on this, P=NP or P!=NP? When do you think it is going to be settled?[link]#

I don't know if this has more touch of philosophy. Do you believe that programming is more of an emergent behavior of math or is it it's own thing which is just well-described by math?[link]#

How has your involvement with music affected your computer science and vice versa?[link]#

You are famously known for your interest in (and contributions to) digital typography. Over 30 years after the release of TeX, what are your thoughts on the current state of typography as it exists on the web and other digital media?[link]#

Now kids are growing up with using computers like on cellphones everywhere - like the small small kids - but the computer became really complicated. What do you think will be the long-term appeal? Will we have more people understanding how it all works? Or are we going to have magic; there are only a few who understand it[link]#

Programming today has not fundamentally changed from programming decades ago. How has the industry failed in this regard and how could it change in the future?[link]#

What do you think is the most effective way to get children enthused about CS?[link]#

Did Steve Jobs tell you he'd read all of your books, and how did your respond? \bye[link]#

So are you familiar with the field of Natural Language Processing? Do you see having any effect on the field of Literate Programming or programming in general?[link]#

Years and years ago when I was in computer science there was a lot more expectation for mathematical training. I noticed that over the thirty/forty years there is less and less dependence on mathematics and my impression is that students are less trained in that. I remembered when Donald Knuth at Stanford for a number of years whether they have a graduate degree in computer science and so forth. And I think that there was a presumption that people should have mathematics training (and so forth) before they went into computer science. How has computer science changed as the role of mathematics has become less in this field? I am interested in your view.[link]#

Which were the real milestone decisions or moments in the history of computer science since you started to work in the field of computers?[link, 04:22]#

If you could ask God 'One Question Answered' which one would that be and why?[link, 11:56]#

Among the great unsolved computer science problems that can be simply formulated and understood by laypeople, which do you find the most fascinating and puzzling?[link, 14:40]#

Are you satisfied with the current status of TeX (and derivatives, namely LaTeX, ..etc.) has become. Was this the image you had in mind when you first conceived it?[link, 22:05]#

Who were the persons who inspired/influenced your work when you were young? As you were a young student, you were (among others) torn between physics, mathematics and computer science. For me, a SOI participant and future student, this is similar and I am interested to know why you chose computer science instead of mathematics and physics. What are the basic differences between that disciplines?[link, 26:16]#

Would you agree (and if so, lament the fact) that there seems to bean ever increasing gap between knowledge and use of computers? Just as with cars, where few drivers today have any notion of the inner workings of a combustion engine, it seems that computer users are happily oblivious to what goes on 'inside'. Is this in your view an achievement or a shortcoming of computer science in the past 50 years?[link, 33:22]#

How do you see the world in 50 years? What are your thoughts on the future of the computer world? What will it be like in 10 or 50 years? How do you think society will deal with the gaping pace of technology?[link, 39:25]#

Do you think it's good that in the last time some computer science diversity is vanishing? If you look like 50 years ago the machines / operators… we had SPARCs, MIPS, Alphas and now every computer is Intel-compatible and even farther in the history you will find even the computer operating on 9 bits and now it's nearly all standardized. It's nearly all Intel-compatible and there are niche exceptions like embedded which are still somehow similar. Do you think that it's a good thing that the computer side wall experience a conversion to nearly single architecture?[link, 42:22]#

Concerning sorting and searching... what about the concept that you use entropy of the things that you search and sort and make use of knowledge about what you are. Could that improve the algorithms?[link, 47:21]#

Do you think that quantum computing could dispone a new conceptual paradigm for computer science?[link, 49:20]#

If computing were to adopt ternary logic. How do you see the future of the field changing?[link, 51:41]#

So on your webpage you say that you can tell The Art of Computer Programming as your most important work of your life. I mean I am grateful for having those books but a lot of people in the field were considered solving open problems. Did you have at same point made a choice between the two or did you always wanted to kind of spend your time [on writing]?[link, 54:39]#

Based on your experience what are the most challenging and interesting fields of computer science for the next 5, 10 or even 15 years? Or if you are 20 again: What would you choose?[link, 57:52]#

So you spoke a lot about bringing mathematics into programming and also institutionalizing the practice of proving that algorithms work and so on. I was wondering how far are we from institutionalizing in the other direction where you use computers to help formalize mathematical statements and compute them on an even more rigorous basis?[link, 59:31]#

As you probably know the mathematicians have always have natural key open problems that they can present to the public. That's a very simple open problem that they can present to the public. That's a very simple open problem that's very easy for folks to understand and they can get people to think about deep questions. I guess it used to be from last-last year (unfortunately there is no longer an open question); so I guess the leading question these days is - let's say - the Riemann hypothesis. Maybe not that easy to understand but still fairly easy to state. So my question to you is, if you want someone to get excited about algorithms, what would you use as the nice, beautiful, open problem to present?[link]#

In the 1790s the French tried to introduce a metric time system. Yesterday I was reading the article about leap seconds in the Communications in the ACM. So we have leap seconds sometimes in June and in September, because the earth is not rotating exactly 24 hours. So how would a computer scientist design a time system taking into account the fact that we live here on this earth?[link]#

So what could still be done in the computer science world that you would feel would provide a greatest impact to humanity? What is left to discover, build or create?[link]#

Do you spend much time reading on the internet? And if you do, which sites do you read?[link]#

For my classmates at the university of Waterloo in Canada I find it increasingly that not many people know who you are or what you have done. Do you think that is a problem?[link]#

I wonder I have read that you don't like to use email?! So these days facebook and twitter is everything. So do you use it or you don't?[link]#

You developed TeX at a time when computers where slow and WYSIWYG word processing did not exist. If you would develop TeX today would you make changes, because of how computing in this place in this world?[link]#

We learned Pascal in the 80s. I moved on. I learned C. Then I learned C++. I doubled in Java. I have done software basically for 25 years. I still think it's hard to write. Any thoughts on how we can make software development easier to write? fast to write? less error-prone? easier to debug? especially with coming multi-threading around?[link]#

The question about the application side of mathematics and computer science. So do you think it's possible to build a comprehensive mathematical or computer model of modern economics where you can throw in certain variables and get the prices for what you put in later on. If not, why?[link]#

What's opinion of quantum computer? And if someone builds a quantum computer, are we basically going back to the drawing board as far as algorithms are concerned? And what does that mean for the books?[link]#

Back when I was a student here some of the political aspects of some of the algorithms… back when I was a student here RSA came out. There were controversies about. Fiber stuff. And then PGP - pretty good privacy. And then later they had napster, but napster got shut down. So they made Bittorrent which is distributed (peer-to-peer). So there is no middle-man. And now there is something called Bitcoin coming along which is a completely distributed no-middle-man digital crypto currency. So I was just wondering if you can follow to any of those trends and what you have to say about that?[link]#

Your website has Frequently Asked Questions. It also has Infrequently Asked Questions. Do you have any idea why those are Infrequently Asked Questions and why did you feel the need to ask them?[link]#

Could you share with us a memorable mistake you made in the last year that you learned from it?[link]#

If you were starting out as a PhD student today; what area of computer science do you think is worth working in?[link]#

Do you think we will ever create an actual artificial intelligence? One, capable of self-awareness and able to increase its own intelligence exponentially like in singularity?[link]#

We have lots of these famous problems in computer science such as P vs NP. But what do you think is the biggest bottleneck in our understanding of computational sciences to improving quality of life with computer science?[link]#

What is your general approach for solving tough mathematical problems?[link]#

I am also a graduate student here more than a year ago. And I am now at faculty at Delhi Institute which is in India. Professor Knuth is not only as a great computer scientist but also as a great teacher. So my question now is that for the several years the rule of a teacher is changing from that of a traditional teacher to a facilitator because almost all the information that a teacher can probably pass to its student is already available because of the information explosion. What are your thoughts on that and then what would be your advice for young students?[link]#

What are your thoughts on Open Access journals as opposed to Subscription journals; Open Access textbooks as opposed to paid textbooks all can be delivered over the internet. How do you see playing that out? Can this [Selected Papers on Fun and Games] be downloaded?[link]#

What are your perspectives on the increasingly fractured state of academia and what would you change if you had the power?[link]#

This question concerns your stance as the manager of the basketball team at Case Western. And I saw a video which claimed that you used some really good math to get good results for your team. Could you briefly discuss that and tell us what…[link]#

You look at problems. You solve some. Any you analyze others. My question to you is: What is reaping your heart? What do you like more? The solving of problems or the analysis of a more healthy problem?[link]#

I think something like 35 years or more ago I remember you saying that computer science did not have enough deep results to qualify as a real science. And my question is: Are we there yet?[link]#

So you write programs. What programming language do you like the most?[link]#

How can you look cool in front of other engineers by believing in god and also being a nerd, I mean?[link]#

I am looking for more ideas for adult sunday school. I take quite a few ideas from 3:16. So I am teaching resampling chapters from the bible. I have taught classes where we translate verses from Greek and from Hebrew. I am going to do statistically significant words to take out the themes. My tool chest… I need more things to… more approaches.[link]#

You mentioning talking about faith and science at MIT reminds me of something Evelyn Fox Keller sensed. She is a physicist who became a scholar of science and she went from teaching at Berkeley to teaching at MIT. And she said at MIT she had trouble getting students to see that there is a social impact on what science is created. And at Berkeley she had trouble getting them to understand that there was anything but the social. But my question is about evolution. With Darwin's 200th birthday and so few Americans believing in evolution and there is still being conflict about what's taught in the public schools. I want to ask what you believed and what you think should be taught. What's behind the disagreements?![link]#

My partner who - like you - is a Lutheran and astronomer once gave a similar talk and on the question of 'how did his faith influence his science?' he had a blank slide. You know, he has to feel the need to keep his faith and science separate. And on the other hand you have got people like Richard Dawkins who claim that faith gets in the way of science. How do you personally answer this questions. How do you personally answer this question? How do you feel your faith influences your science?[link]#

Instead of just your personal views; what do you think of the notion of if you have a belief that they maybe dictated by the reading of the bible. Just somebody in general. For example they might be certain about an embryo and whether or not harvesting is a murder or not. Taking this to the next level, how much effort should a person (that has that belief) put into like getting that belief implemented in policy and society? [link]#

I am strucked by your use of the term faith in the title of this talk. I don't know anything about your theology prior to hearing this talk announced and coming here hearing your remarks. If the talk had been titled (for example) 'God and Science' or 'Theology and Science' than I could see how that would be perhaps where you and Dawkins might have a disagreement on where the preponderance of evidence is and where this could be an implication to discussion in debate. But the idea of faith is really one that very much puzzles me. First of all, the odds of some of the things I hear you saying today which is the searching, the sampling, the investigation, … It seems to me like you still are looking to examine evidence and to react to evidence?! Whereas I take the doctrine of faith to be a proud immunity to evidence?![link]#

Is the human brain a computer? And if so, what are the theological implications?[link]#

Do you think that today's ordinary people need more faith than people centuries ago and maybe this is the reason for what seems to be that irrationality is taking over again. I explain my question: For me when I understand something I know it. I don't need faith. I need faith when I don't understand something. Now it seems that in the medieval time ordinary people knew much more portion of this scientific knowledge of that time. They just went to the church. They heard from the priest the word of God, but also some scientific knowledge: God created everything. Earth is the center of the universe and things like that. But today's scientific knowledge is so wide. Ordinary people… well, even scientists know a very small portion of it. So maybe we need faith?[link]#

I was wondering if you could say a few words about how you come to believe what you believe both in terms of physical and spiritual matters. Say… what your basic preconceptions are; about knowledge; maybe experiences that you have lead to believe what you believe. And I am also a little bit intrigued that the 3:16 project with this kind of idea of random sampling especially as I kind of think about creating a world view and trying to make sure that everything is coherent and realizing that bible verses and all that knowledge have a context to them.[link]#

I was wondering about how you synthesize all kinds of knowledge into a coherent world view?![link]#

There is an essay you did a while back called 'The errors of TeX' in which you logged every single bug you had while working on TeX. And you went backward and analyzed the patterns. This always strucked me as a deep exercise in melody. And I was wondering if you thought it'd came from your christian background or it's just the right thing to do.[link]#

[…] So one of the things we have come to understand is the sort of an understanding of evolutionary biology and personally for myself watching people over my thirty odd years of life, it seems like that a lot of human behavior is at least understandable in light of the fact that we have deep structures whether these are biological or semantical structures within our brain that cause us to believe or act in certain ways. Some good examples of this: Kissing a pretty girl (seems like that I have structures in my brain that make me wanna do that), moment of enlightenment when you see a beautiful proof or have a very remarkable result ([…] certainly something inside my own brain makes me want to see God or something like that), listening to a cantata by Bach. That's pretty clearly a result of a man who was deeply religious and used it to do something exquisitely beautiful. In each of these cases tough there is a good examples of the fact that there is stuff in our heads that makes us believe things. It sure seems like that religion is that way. And the reason for this question that I ask it, I don't think it's necessarily bad that we have these structures in our head that make us tend to believe things because good things come out of it, right? But at the same time I have another deep structure in my brain that makes me seek out what sort of… intellectual rigor. […] Maybe it's the case that you don't believe that there are deep structures in our heads that make us believe things […] but I suspect that you kind of notice this as well. […] How do you reconcile your faith for the idea […]?[link]#

I am surprised that you mention mystery and wondered as a reason for religion. As the previous person asking the question listed so many cases in the secular world that have both mystery and wonder. But my real question is: If God asked you something dire would you do it?[link]#

So my question is: What's your favorite algorithm? And because Don answered this question to me before and said 'Euclid algorithm' I restrict it to algorithms invented in the last 100 years.[link]#

Is computational/algorithmic thinking something that one knows when he sees it or can it be explained?[link]#

Professor Knuth, I want you to consider the following situation. [laughter]. A talented young person is planning to enter university, but he or she is not yet sure what to study. The person takes studying computer science into consideration. Now the person asks therefore you why should I study computer science and what are the (let's say) 3 most important things or results I can learn in doing so. What would you answer?[Gödel Lecture, 00:14:19]#

Professor Knuth, you are known for opposing software patents or intellectual property for algorithms as such. Can you give us a brief outline of your arguments?! And does your position imply that open source project should be prevalient (in industry)?[Gödel Lecture, 00:21:15]#

Professor, how do you envision the future of artificial intelligence? Do you think future intelligent computers will just be suiter intelligent machines or will our minds maybe sometimes be extended by machines. Similarily to the ones that were described by in Isaac Asimov's ‘The Last Question’.[Gödel Lecture, 00:29:00]#

[First of all, I hope that you won't pass away too soon. Because then we will have the first time when a system will have an infinite version number and I don't know whether people have thought about that problem. So you know the number PI will be the final version number of ΤeX. Should we try to enumerate one-hundred digits after the decimal-point?! I don't know how we can do it. But my serious question or rather little bit of tongue-in-the-cheek question:] Many years ago—or from Mister Zemanek's point of view only a few years ago—I bought The Art of Computer Programming. I was very impressed by these thick volumes. Ever since then I was wondering what we are really doing: Is it computer science or rather computer art? Or partially translated to computer ΤeX?[Gödel Lecture, 00:31:54]#

Professor Knuth, is there some result or accomplishment in computer science that someone else made, but you really wish you have made? And if yes, why do you really wish you have made it?[Gödel Lecture, 00:36:36]#

I have a transatlantic question. What is the difference between computing (as established in ACM or your person) and information processing (established in IFIP and Professor Zemanek)?[Gödel Lecture, 00:40:14]#

Good evening, I would like to ask you which big challenges in computer science or IT you see where we should be working on? So where you wish we should progress or which are promising.[Gödel Lecture, 00:43:52]#

Thank you so much for being here. I enjoy your research so much. My question today is the one about programming language design. So you are the author of TeX and the WEB system. You have written many source codes in Algol, Pascal… you even published a source code in INTERCAL and you also have been quoted to tell at the ACM Turing 100 Banquet that python is the only popular language which is not ugly. So my question here is today, uhm, what are your personal criteria for what makes a programming language beautiful?[Gödel Lecture, 00:47:44]#

Good evening, earlier this evening you talked about the type of thinking required to do computer science. Since I am mathematics student and you also wrote mathematics like your book ‘Concrete mathematics’. I was wondering if you think there is a difference between the type of thinking required to do mathematics versus the type of thinking required to do computer science?[Gödel Lecture, 00:52:52]#

What should children learn in primary and secondary school about computing and information processing?[Gödel Lecture, 01:00:20]#

Professor Knuth, how do you imagine the solution to the P-vs-NP problem?[Gödel Lecture, 01:01:15]#

Hi, any structures in mathematics or computer science that surprised you being equivalent to another mathematical or computer science structure? Like Game of Life being turing-complete. Or like a finite automaton is equivalent to a regular language?![Gödel Lecture, 01:03:46]#

It's kind of a meta-question: If you were a student here in Vienna, what would be your question to Donald Knuth?[Gödel Lecture, 01:12:38]#